1. Field of the Invention
This invention relates to an eye fixation monitor, and particularly to an eye fixation monitor for monitoring the fixation of an eye that is being examined using a perimeter or the like.
2. Description of the Prior Art
When using an ophthalmological examination apparatus such as a perimeter, it is important that during the examination the patient's line of sight is fixed on a target and for this eye fixation to be maintained for a specified period of time. The reason for this is that in the examination of a person's visual field the eye fixation target is used as the basis of reference for setting the coordinates. Therefore, if during the examination the line of sight deviates from the eye fixation target, it becomes difficult to measure the visual field.
As a method for monitoring whether the eye fixation is being maintained, there is known the method according to Japanese Laid-open Patent Application No. 60(1985)-97928, in which an optical system is used to form an image of the eye being examined, a plurality of photoelectric transducers are arranged at the position where the image is formed, a switch is provided to zero the initial value of the outputs thereof as the eye fixation state, the ophthalmologist conducting the examination operating the switch to zero the initial value while using a viewfinder or similar means to confirm the eye fixation state, following which the eye fixation is monitored.
With the aforementioned conventional type of apparatus, there are cases where the eye fixation becomes defective owing to deviation of the fixation of the patient's eye during the examination, and also in cases where the person being examined moves his face, the photoelectric transducers will function as if the eye fixation has become defective so that, notwithstanding that the patient's eye may be fixed on the target, the examination has been suspended on the grounds that the eye fixation has become defective. In such cases, it is necessary for the ophthalmologist to reconfirm the eye fixation state and operate the switch for zeroing in that state. Therefore there has been the problem that the ophthalmologist has to remain on hand by the apparatus until the completion of the examination.